Production of wood preserving impregnants



July 28, 1942 J. E. HARVEY, JR 2,291,295

PRODUCTION OF WOOD PRESERVING IMPREGNANTS Filed June 20, 1940 #V000 Pfaff/PVA r/z/E (Uva P/QoDf/crj Patented July 28, 1942 UNTLED STAT-S 'i' .OFFICE PRODUCTION l0F WOOD :PRESERYING IMPREGNANTS .Jacquelin'EH Harvey, Jr., Atlanta,eGa., assigner of one-half to Southern Wood Preserving Company, East'Point, Ga., a corporation o'fGeorgia `-7 Claims.

The Vpresent invention relates to thegproduction of useful products from tars of all "classes, as for instance coal tangas house tar, y10W temperature tar, water gastar, vblast :furnace tar, lignite tar, wood tar, ,pine tar, aromatic and partially aromatic tarsederived from extraction or polymerization of petroleum yor petroleum fractions, including gas or gases; .and pitch and residues derivedftherefrom.

By the terms pitch and residuesmasused in the following specification and appended claims is meant that portioncf `tar resulting from the removal, as for instance-by'distillatiorr'extraction or the like, vof Yfractions :of said tar which produces induced viscosity in the residual mass. Thus, the terms pitch and/ or residue includes 'fractions of tar which are more .viscous than said tar. 'As an example, the vpresent invention views that residual massof vsaid tar resulting from the removal of, as for instance, heavy naphtha with an end point of say 290 C., aspitch or residue.

An object of the present inventionlis the production of wood preservatives from tars and/or pitches derived therefrom.

A further object is the controlling of the characteristics of said wood/preservatives.

A further Objectis the enhancing 4of toxicity in hydrocarbons, orliquids and/or solids oonl inducing-,reaction conditions to those fractions of the starting materials outside, or substantially outside, the range generally accepted for toxicity measurement.

Another Y object of the present invention is the enhancement of toxicity-inducing conditions .by the elimination, at least to a degree, of Ithose fractional materials'held under reaction conditions that loWer,lor tend yto loWer,-toxicityin ducing conditions on those fractions ofvsta-rting material most in need of toxicity enhancement.

Still anothercbjectof -the present invention is the cie-polymerization,ofv molecular complexes, as for linstance the higher .boiling -fraction or fractions ofthe chosen startingmaterial, whereby to produce a condition insaid molecular complexes that -allows more intensive toxicity-inducing `conditions thereon.

Another object'of the present invention is the `provision of depolymerizing conditions in any of the starting materials `with the added provision of added toxicity-inducing conditions While .re-

taining the starting material substantially under -derived vfrom coal and .petroleum vare .commer- `-cially obtainable inmuch larger.quantities and are therefore the .preferred ,starting ymaterial. This preference, however,.is not to be .construed asia limitation 0n usable starting material for it has been. determined that allaromatic, or partially ,aromatic `tars, lend .themselves to the toxicity-inducing .conditions of the Process.

Thus,.usable starting materials of thepresent process are aromatic tars, pitches and residues .derived therefrom, .and tars ofless than total ,aromatic content, pitches andresidues derived therefrom.

Thus, itis of importance .to nnte that the present invention broadly coversthe inducing of toxicity, as hereinafter described, in tars'having less than total aromatic content, as for instance Water gas tar and other utars derived from petroleum or petroleum products, such as produced by or from extracted or polymerized products of said petroleum.

An important industrial application of the process of the present invention is to coaltar or products derived therefrom.

By far the greatest volume product sold from coal tar is creosote. There is annually averagely produced in Vthis country Vin the order of 000,000,000 gallons of coal-tar. Asiswell known inthe'in'dustry,if the'aforementioned 600,000,000 gallons of coalftar were `distilled to yieldaverage quality creosote, said quantity of 'creosote would result in'this country being-self-suiiicient in-its creoso-te and refined coal-tar wood preserving needs, say in the order of 175-225 million lgallons annually.

Such, however, is I not' economicallyv possible for the reason that theA creosoteproducer must conne himself to 4that production of creosotewhich amounts to thecorresponding 'quantity-of pitch he 'can 'market at a prot. Pitch being the residualrnass in the still afterthe-creosote has been recoveredfromsaid tar. Pitch has va lim- VWhile held at substantially 250 ited profitable outlet, the net result of which is that domestic creosote producers must content themselves with a total production of creosote that is less than national consumption. Thus, from said condition obtaining flows the necessity of importing many millions of gallons of creosote.

The foregoing analysis of coal-tar economics was made by S. P. Miller, technical director, The Barrett Company, New York, in his Well-known address before Franklin Institute, Philadelphia, Pa., in December, 1932. Y

Many proposals have been made to convert larger percentages of coal tar into acceptable wood preservative to the end that this country would be independent of imported wood preservatives. The Direct Recovery Still was one of the notable proposals to recover from coal tar increased amounts of creosote. This still did recover larger yield of distillate which was termed creosote; however, because the distillate was so high in residue above 355 C., many creosote consumers rejected same. Thus, the Direct Reco-very Still leftmuch to be desired.

As stated in the foregoing, it was, and currently is, a desderatum in the art to recover increasingly larger percentages of creosote or wood preserver from coal tar. Volume for volume yield of wood preserver from coal tar being the ultimate goal.

In my former Patents 2,082,885; 2,113,589; Reissue 21,438; 2,191,466, and 2,185,413, I recite methods for securing from coal tar, or the like, from substantially 80% to 100% of coal tar conversion products that are usable as substitutes for creosote and creosote-coal tar solutions, that is to say creosote in mixture with coal tar.

,The afore named patents describeprocesses for subjecting tars, pitches and creosote to toxicityinducing hydrogenation whereby to, among other things, more nearly approach. volume for volume V,conversion of starting material into the desired product, as for instance wood preservative.

The aforementioned patents are, among otherV things, predicated on hydrogenation controls that induce toxicity. In the forenamed processes it has been found that as the processes were carried forward, that the synthesis of toxicity did not remain constant, even though reaction conditions were unvarying.

The present process provides for, among other things, a process which re-institutes, to at least a degree, the original synthesis of toxicity on the starting material, at the time of, or after, said synthesis decreases, that is to say, fails to hold at the initial high rate.

The invention will be understood from the following description of illustrative steps comprising various methodsof securing the objects of the invention, when read in connection with the accompanying drawing wherein the gure is a diagrammatic sketch of an apparatus for'carrying'out a forrnof the process of the invention and wherein the Vnature of the step carried out in each chamber and the contents thereof are indicated by legend.

Egzmple Z.-Coal tar having in excess of 8% coke residue ,and boiling predominantly above 190 C. isV subjected to the action of hydrogen atmospheres pressure and 410 C. After said temperature and pressure had been attained, it was then found that the synthesis of toxicity reached a peak value, and thereafter with reaction conditions remaining constant, the rate of toxicity synthesis approached zero as a minimum.

After experimentation and research it was found that those induced fractions in which toxicity had been synthesized actually acted as a blanketing effect on those fractions from Which it was further proposed to synthesize toxicity. That is to say, that as toxicity was synthesized as flowing from fractional increment adjacent to and below 270 C., that the presence of said induced fractions actually lowered the rate of toxicity synthesis. It was found that by removing a portion of the lower boiling fractions and re-instituting original reaction-conditions, that the synthesis rate of toxicity was enhanced, that is to say, the inducing of lower boiling fractions from those fractions boiling adjacent to and/or above 270 C. was increased, or stated another way, toxicity was synthesized.

The re-insituting, wholly or partially, of the original high rate of toxicity synthesis is accomplished by removing fractions up to 230 C. However, beneficial results are secured by removing a smaller percent of said lower boiling fractions; on the other hand, fractions up to 270, 280 C. or higher may be removed for the desired purpose.

After removal of said fractions, the residual mass is then returned to the reaction system and original reaction conditions impressed, or they may be more severe or less severe, and continued for such a length of time as induceia low boiling point which conforms to any of the wood preserving oils currently sold to the trade, as for instance:

Specification: I. B. P,

American Wood Preservers Association 5% at 210 C. Do 1% at 210 C. Do 11/2% at 235 C. Prussian Ry 3% at 150 C.

Neville Shingle Stain Oil C. Southern Pine Shingle Stain Oil 92 C.

In the event too great a percentage of low boiling ends is produced, the material may be stripped to make same conform in its low boiling range to the desired specification.

The newly formed oil may be used en toto as a substitute for a creosote-coal tar solution or stripped oi' some of its high boiling fractions to provide a substitute for creosote. In the option last named, the residue may be used as an article of commerce,.or if desired, returned for recycle operations.

Looked at in one manner, the present invention broadly includes depolymerization of high high pressure system; as for instance, streaming gas or the hydrogen of the process may remove by entrainment the low boiling fractions or par- Vtial release of pressure may flash the desired fractions.

Temperatures ,from 100 ,C. ;are'.usablev as: are pressures fromatmospheric and upward. lHowever, to approximate commercial .operating necessities, elevated temperatures and pressures are desirable. Good results when usingy coal tar have been secured by temperatures of 460 C..and above, and pressures of 200 .atmospheresand above.

Catalysts assist in speeding andv directing the desired reaction of the :process of the present invention. All hydrogenating catalystsare usable, but those having .substantial sulphur poisoning immunity are desirable, as for instance, metals of the 6th periodicgroup orcompounds thereof, such .as suldes. .Various catalyst forms may be used, such'as various shapes; deposited in well-known manners on carriers; cobalt, tin, molybdenum, vanadium, chromium, or compounds, ypromoted or infadrnixture; as for instance with small amounts of -acids or halogen derivatives; all catalysts of known hydrogenating ecacy, in the form of shapes, pellets, extruded lengths, comminuted, deposited on car riers, with or without the presence of other materials possessing hydrogenating properties, or not, such as asbestos, lumps-of brick, quartz, etc.

Selective catalysts may be used; for instance '1 a selected catalyst, or form of catalyst, may be used for the period whose end is `characterized by reduction in toxicity synthesis; thereafter, and for the period characterized by prior removal of loW boiling fractions a different catalyst, A

its entirety, if desired, is converted into a usable wood preservative with the added benet'that the initial high rate of toxicity synthesis is reinstituted, at least to a degreeyafter said rate of synthesis has been reduced.

In the foregoing example, and .those followl ing, recourse may be had to Athe blending of the rst removed fraction following' toxicity synthesis reduction with the later formed .wood preservative, thus forming an overall wood preserva-- tive, with the low ends thereof being stripped, if desired, to make said overall oil conform to any of the low ends'of specification oils cited; or to conform to the low endsof any desired preserving oil.

Broadly considered, the present vinvention .is not circumscribed by the necessity of making the product thereof conform ,to current Wood preserving speciflcations, but is so fiexible as to enable production of any desired wood preserving oil as regards lowends, residue at any given point, coke residue, specific gravity, viscosity and float.

Among other things, the toxicity synthesis of the present 'invention flows from .reduction of their the second hour. lfrom the reaction zone and stripped of its low coke residue and'increment oflfractions boiling adjacent to and below 270 C., and the .novel manner, .above described, of re-instituting at least to a degree, of said toxicity synthesis.

Example 2.--Pitch is one of rthe preferred starting materials of the present invention. By the term pitch is meantv any-fraction of forenamed tars, or the like, whose viscosity and specinc gravity are greater than ksaidstarting tars, as for instance heavier fractionsinduced by removal of low boiling fractions -such as by solvent action or distillation.

A coal tar pitch, 15% boiling'at 355 C., specic gravity in the order of 1.23 was subjected to the action of hydrogen under 275 atmosphere pressure and 375 C. under agitated conditions. Tests determined that the rate of toxicitysynm thesis was a decreasing quantity at the end of The pitch was then removed boiling fractions up to 285 C. YThe Stripped pitch was then returned and heldunder'the, action of hydrogen at 275 atmospheres-andl400 C. for one hour. 'Ihe original high rate of .toxicity synthesis was re-established, at least to adegree. The beneciated mass was found to` distill in its lower end in a-ccordance with van vA. W. P. A. creosote-coal tar solution oil, thatis'to-say,not more than 5% at210 C. Other-physical characteristics made same usable asas-ubstitute for a creosote-coal tar solution oil of the 70-30 type.

rBy the term beneciated is meant any of the starting materials atleast oncesubjected to the action of hydrogen.

It has been determined that the crude start ing materials once subjected to the action of hydrogen, have been depolymerized, especially in the higher .boiling fractions, to such extent that they are less susceptible to thermal degradation than the parent materials. vWhatever the usual definition of depolymerization, the present usage includes the addition of hydrogen to the high molecular complexes, with or without reduction in size of said complexes, as for instance any of the higher boiling: fractions of the starting material, including pitch.

During the period of toxicity synthesis, in the event undesirable llow ends havebeen formed, same may be stripped to make said oil conform in its low boiling endvto the 'desired wood pre serving oil.

The low ends removed for the purpose of reinstituting, to at least a degree, of the original high rate of toxicity synthesis, may be added to the residue of a plurality of said stripping steps, which residue has been beneficia-ted by the process to form an overall Wood preserving oil, with removal, if desired, of any percentageof lowboiling oils to make same conform to any current specification, as for instance the usual boiling ends in a carbolineum; or, any desired private specication.

Example 3.-Sorne rpitches which it is desirable to use as starting materials for the process of the present invention are in such a polymerized condition as to make necessary less vigorous thermal conditions at process start. ofcourse, such procedure is entirely possible, with increase of thermalconditions as the depolymerizaticn proceeds. An alternative is to first depclyrnerize the pitch with a solvent, as forinstance petron leum or coal tarsolvents. Such alternative prou cedure allows more vigorous thermal conditions and the process goes forward with greater rapidity.

At the point in operations, or thereafter, when toxicity synthesis decreases, re-institution is accomplished as aforenamed.

The stripped beneciated mass is now partially depolymerized and thus not so susceptible to thermal degradation, and may be charged back to the process without solvent addition.

Concerning percentage of solvent necessary, a small percent is beneficial and up to volume for volume, or more, may be used.

At times it is desirable to use a solvent that is substantially inert to the conditions of the process, as for instance a refractory solvent, or the like.

Example 4.--Another starting material for the process is creosote, as for instance high residue creosote. Many processes for creosote recovery from coal tar push the distillation to such points that the residue in the creosote above 355 C. is so high that many consumers of creosote refuse same because of said high residueA The high residue creosote is treated in accordance with the present invention to produce the desired wood preserving oil.

Thus, from the foregoing examples it will be seen that the present invention broadly includes a novel method for compensating, at least to a degree, for decrease in toxicity synthesis, that is to say, impediments to maintenance of toxicity synthesis rate are removed, partially or totally, and said toxicity synthesis rate is re-instituted, to at least a degree.

The term pitch as used herein and in the appended claims includes the higher boiling fractions of tar, in other words tarA from which low boiling ends have been stripped, such lowboiling ends being suitable for use per se as creosote= other wood preservative or solvent. For instance the final residue resulting from evaporating tar to dryness (coke) and then stripping wood preservative from the distillate is a very suitable pitch for use as a starting material of the present process, as such, cut-back or otherwise.

Intermittent or batch operations well known to the art may be incorporated in any or all of the foregoing examples and minor changes or obvious equivalents substituted in the steps of the process within the scope of the appended claims without departing from the spirit of the invention.

I claim:

l. In the production of wood preservative impregnants from a mixture of tar fractions of aromatic content the process which comprises: subjecting said material to the action of hydrogen with time, temperature and pressure so controlled as to produce wood preservative fractions of induced toxic value and with consequent reduction of rate of synthesis; stripping from the treated material newly induced low boiling material to produce a residual having an initial boiling point in the range of about 230 C. to about 285 C.; continuing reaction conditions on the stripped residual with resultant at least partial restoration of rate of synthesis and With time, pressure and temperature so controlled as to produce an oil of the wood preserving type having no greater percentage of materials boiling below a given point than is permitted by specifications accepted in the trade for a tar derived wood preservative, said wood preserving type oil being further characterized by a substantial residue above 300 C.

2. In the production of wood preservative impregnant from a mixture of tar fractions of aromatic content the process which comprises: subjecting said material to the action of hydrogen with time, temperature and pressure so controlled as to induce newly formed low boiling fractions of synthesized toxicvalue with consequent reduction of rate of said synthesis; stripping from the treated material newly formed low'boiling material to produce a residual having an initial boiling point in the range of about 230 C, to 285 C.; continuing reaction conditions on the stripped residual with resultant at least partial restoration of the rate of synthesis and with time, temperature and pressure so controlled as to produce an oil of the wood preserving type which if relieved of a percentage of its low boiling fractions will have no greater percentage of materials boiling below a given point than is permitted in specifications accepted in the trade for a tar derived wood preservative and will be further characterized by a Substantial residual above 300 C.; and relieving said oil of the necessary percentage of low ends to provide specication conformance as stated.

3. In the production of wood preservative impregnant the process which comprises: subjecting a mixture of tar fractions of aromatic content to the action of hydrogen with time, temperature and pressure so controlled as to produce wood preservative fractions of induced toxic value with consequent reduction of rate of synthesis; stripping from the treated material newly formed low boiling material to produce a residual having an initial boiling point in the range of about 230 C. to about 285 C.; instituting intensified reaction conditions on the stripped residual with resultant at least partial restoration of said synthesis with time, temperature and pressure so controlled as to provide an oil of the wood preserving type having no greater percentage of materials boiling below a given temperature than is permitted by specifications accepted in the trade for a tar derived wood preservative, said wood preserving type oil being further characterized by a Substantial residue above 300 C.

4. In the production of wood preservative impregnant from a mixture of tar fractions of aromatic content the process Which comprises: subjecting said material to the action of hydrogen with time, temperature and pressure so controlled as to induce newly formed fractions of synthesized toxic value with consequent reduction of rate of said synthesis; stripping from the treated material newly formed low boiling.

material to produce a residual having an initial boiling point in the range of about 230 to 285 C.; continuing the stated reaction on the stripped residual at a more elevated temperature, with resultant at least partial restoration of said synthesis and with time, temperature and pressure so controlled as to provide an oil of the wood preserving type which if relieved of a percentage of its low boiling fractions will have no greater percentage of materials boiling below a given point than is permitted by specifications accepted in the trade for a tar derived wood preservative and will be further characterized by a substantial residual above 300 C.; and relieving said oil of the necessary percentage of low ends to provide 'said specification conformance as stated.

5. In the production of wood preservative impregnant from pitch of aromatic content the process which comprises: depolymerizing said material with a solvent therefor and thereafter subjecting the cut-back pitch to the action of hydrogen with time, temperature and pressure so controlled as to produce wood preservative fractions of induced toxic value with consequent reduction of rate of synthesis; stripping from the treated material newly formed low boiling material to produce a residual having an initial boiling point in the range of about 230 C. to 285 C.; instituting reaction conditions of the same character at a, more elevated temperature on the stripped residual with resultant at least partial restoration of synthesis and with time, pressure and temperature so controlled as to produce an oil of the wood preserving type having no greater percentage of materials boiling below a given point than is permitted by specicatons accepted in the trade for a tar derived wood preservative, said wood preserving type oil being further characterized by a substantial residue above 300 C.

6. In the production of wood preservative im.- pregnant from pitch of aromatic content the process which comprises: material with a solvent therefor and thereafter subjecting the cut-back pitch to the action of hydrogen with time, temperature and pressure so controlled as to produce wood preserving fractions of induced toxic value with consequent reduction of rate of synthesis; stripping from the treated material newly formed low boiling material to produce a residual having an initial boiling point in the range of about 230 C. to

depolymerizing said i about 285 C.; reinstituting reaction conditions on the stripped residual with resultant at least partial restoration of synthesis and with time, temperature and pressure so controlled as to produce an oil of the wood preserving type which if relieved of a percentage of its low boiling fractions will have no greater percentage of materials boiling below a given point than is permitted in Specifications accepted in the trade for a tar derived wood preservative and Will be further characterized by a substantial residue above 300 C.; and relieving said oil of the necessary percentage of low boiling ends to provide specii'lcation conformance as stated.

'7. In the production of Wood preserving impregnant from a mixture of tar fractions of aromatic content, the process which comprises: subjecting said material to the action of hydrogen with time, temperature and pressure so controlled as to produce wood preservative fractions of induced toxic value with consequent reduction of rate of synthesis; stripping from the treated material newly induced low boiling material to produce a residual having an initial boiling point not substantially higher than about 285 C.; continuing reaction conditions on the stripped residual with resultant at least partial restoration of rate of synthesis and with time, temperature and pressure so controlled as to produce an oil of the Wood preserving type having not substantially more than about 3% distilling at 150 C. and being further characterized by a substantial residual above 300 C.

JACQUELIN E. HARVEY, JR. 

